Estacado Solves The Push To Talk Riddle

A new open source effort to create a more efficient SIP signaling stack could lead to standardized, Push To Talk services.

Push To Talk (PTT), the walkie-talkie-like feature popularized by Motorola's IDEN service, may finally come to a cell phone near you. An open-source project launched last week introduced the protocol stack that will allow PTT to work across any wireless network implementing SIP signaling.

The project, called Open SigComp, was launched by the SIP brain trust over at Estacado Systems. SigComp is short for Signaling Compression, and what this little puppy of a protocol does is speed up the sessions setup under SIP. That's not such a big deal on fat landlines, but it's a whopper of an issue for wireless systems looking to deliver PTT services that require speedy responsiveness across miniscule data connections.

The Open SigComp project will develop a free implementation of SigComp based on Estacado's code. A 0.9.1 version of Open SigComp is currently available. The version is designed to be used in "highly constrained" environments, such as embedded mobile terminals and high-performance, highly scalable servers.

"If you look at the signaling necessary to set up a call using SIP over, say, 1xRTT networks, it can add 5 to 10 seconds to the call setup times," writes Adam Roach, CTO of Estacado in an IM. "Once you compress the call setup messages, you can cut that down by a factor of 10 that is a half-second to one second instead of five to 10 seconds."

That'll be good news for enterprise end users. PTT has gained popularity among retail, transportation, and other businesses needing to keep employees in close contact with one another. However, today Motorola owns the market. Non-Motorola PTT services, such as Sprint's ReadyLink service, have come under fire for being too sluggish. SigComp should address that problem.